Having completed clinical training in obstetrics/gynecology, I am the recipient of a three year Physician Scientist Award to pursue proficiency in basic science, with the ultimate career goal of research, teaching and clinical practice of ob/gyn. This award is almost over, and I seek two years of MCSDA support to extend my proficiency in molecular biology to that of an independent investigator. The research plan is designed to provide information about the transcriptional events that dictate heart development. We have described a novel subfamily of three GATA transcription factor genes (gata-4,gata- 5,gata-6) that are differentially expressed in the developing heart. The expression of this gene represents one of the earliest known markers of pre-cardiac mesoderm. In addition, the gata-5 gene is robustly expressed in the heart throughout development whereas the gata-4 and gata-6 genes are dramatically downregulated in the heart during the latter half of embryonic development. I have sequenced the promoter and have mapped a number of DNase I hypersensitive sites within and flanking the gene. I propose to characterize the cis-acting elements and trans-acting factors that regulate gata-5 gene expression. I will identify control regions sufficient to direct heart-specific expression of a reporter gene in transient transgenic mice. I will then identify the necessary aspects of such regions in transient transfection assays in primary cardiac myocytes. I have determined that the gata-5 gene is expressed in primary cardiac myocyte cultures and that these cultures are suitable for transient transfection assays. Minimal control elements identified in transfection assays will be further tested in transgenic mice. Since the gata-5 gene is expressed in endocardial cells as well as myocardial cells, these studies will also reveal whether distinct or common control elements govern the expression of this gene in these two different layers of the heart. I believe that these experiments will contribute significantly to our understanding of cardiac development. The sponsor, Dr. John B. E. Burch, is an accomplished scientist in the field of transcription regulation. He is a tenured Member of the Fox Chase Cancer Center, which is an NCI designated Comprehensive Cancer Center, and an Adjunct Associate Professor at University of Pennsylvania Medical School. He is also on the editorial board of Molecular and Cellular Biology and is a member of the NIH Biological Sciences 2 Study Section. The Fox Chase Cancer Center affords an outstanding academic environment for training in basic and clinical science.